This invention concerns a method of making a preformed taphole and a refractory composition for use therein.
Tapholes are openings, usually round, in the wall of a melting furnace such as a BOF furnace or other metal melting furnace through which metal and/or slag can be poured when the furnace is tilted or when a plug or other closing device in the taphole is removed. Tapholes are generally made of refractory material which is compatible with the refractory material used in lining the furnace or other molten metal container.
As the steel or other molten metal pours through the taphole, it causes wear on the refractory making up the taphole. Generally, the refractory making up the taphole wears much faster than the refractory making up the furnace lining and therefore the taphole has to be replaced on a regular basis during the life of the lining.
While it is possible to repair the taphole in place, for example by gunning refractory around a form placed in the old taphole (which has become enlarged by wear), such repair is less than totally satisfactory. Since such repairs have to be made on a hot furnace (it not being economical to cool the furnace down to make the repair), the refractory forming the repaired taphole is of lesser strength and density, due to the increased amount of water required to gun refractory material, and hence will last for an even shorter time, than a taphole formed by methods such as casting or pressing, methods which result in greater density and strength but which cannot be used to repair a hot furnace.
Accordingly, it has become the practice to preform refractory tapholes and then place them in the furnace to be repaired, the preformed taphole being held in place by, for example, refractory material gunned around it.
Generally, such preformed tapholes are made by forming suitable refractory material, for example by casting, about a hollow metal pipe used as a form. In the first few seconds that molten metal flows through the taphole so formed, it washes away the metal and thereafter the refractory channels the metal flow.
This invention is concerned with a method of making an improved preformed taphole and particularly with a refractory composition useful in making such an improved taphole.